This is the first I've heard of PS4 not supporting DLNA and I'm on GAF all day urry day. Oddly enough, streaming to my PS3 has been the majority of its use for a long time now. Prior to the Last of Us I played Journey and before that I believe it was Castlevania? Creating a device that is to be the center of your entertainment hub in 2013 means that it needs to communicate with your home pc and allow you to access your media: movies, tv shows, photos, etc.
If SteamOS integrates media streaming and support then that is a huge pro to just going htpc / steambox in my living room this coming gen.